The present invention relates generally to a template positioned in a well bore and, more particularly, to a template or system of templates having a configuration which enables circulation of fluids through the template when placed in a main well bore and having alternate configurations which enable drilling and completion of offset well bores through the template from the main well bore.
Well bores are commonly drilled into subterranean formations at an orientation which deviates from true vertical to increase hydrocarbon production from a given well and/or to reduce the unit cost of hydrocarbon recovery from a given well. For example, a deviated well bore penetrating a fractured formation can increase the drainage area defined by the well bore to substantially increase hydrocarbon production from the resulting well. The use of deviated well bores also increases the number of well bores which can be drilled and completed from a single offshore drilling platform having a set number of drilling slots. The ability to recoup the substantial fixed cost of constructing the offshore drilling platform is often enhanced as a function of the number of well bores which can be drilled and completed from the platform. A plurality of deviated or offset well bores can be drilled from any one drilling slot on an offshore drilling platform using current technology as evidenced, for example, by U.S. Pat. No. 5,330,007. A downhole template is employed to guide the drill string in a desired direction which is offset from the surface casing for the purpose of drilling an offset well bore.
The present invention recognizes a need for a downhole template which can be positioned and cemented in a main well bore to enable drilling and completion of an additional offset well bore from the main well bore using the template. One of the problems encountered in developing such a template is to define template configurations and procedures which more easily and cost-effectively enable circulating fluids past the template in the main well bore to cement the template therein and which also relatively easily and cost-effectively enable drilling and completion of an offset well bore using the resulting cemented template. Accordingly, it is an object of the present invention to provide a downhole template or system of downhole templates which is configured for circulating fluids past the templates when placed in a well bore. It is another object of the present invention to provide a process for circulating fluids past the template or system of templates in a main well bore, particularly for the purpose of cementing the templates in the main well bore. It is yet another object of the present invention to provide a template or system of templates which is reconfigured for drilling and completing one or more offset well bores from the main well bore. It is still another object of the present invention to provide a process for reconfiguring the template or system of templates from a fluid circulation configuration to drilling or completion configurations. It is a further object of the present invention to provide processes for drilling and completing one or more offset well bores from the main well bore using the template or system of templates. These objects and others are achieved in accordance with the invention described hereafter.
The present invention encompasses an individual downhole template, a system of such individual downhole templates, and processes for using the template or system of templates in a well bore. In accordance with one embodiment, the invention is a template positionable in a main well bore and configured for drilling an offset well bore from the main well bore. The template includes a body having a proximal face and a distal face, wherein the body encloses a primary chamber. The template also includes a tubular inlet leg engaging the proximal face and aligned with an inlet opening in the proximal face, a tubular main outlet leg engaging the distal face and aligned with a main outlet opening in the distal face, and a tubular offset outlet leg engaging the distal face and aligned with an offset outlet opening in the distal face. The body is substantially cylindrical and encloses at least one by-pass tube extending from the proximal face to the distal face in fluid isolation from the primary chamber. The inlet leg is free from intersection with the main outlet leg or the offset outlet leg within the primary chamber. The inlet and main outlet legs are coaxially aligned about a substantially vertical main axis, while the offset outlet leg is substantially parallel to the inlet and main outlet legs. The template can also include a diverter positioned in the body to define a drill string path from the inlet leg to the offset outlet leg or to the main outlet leg. The diverter can also be positioned in the main outlet leg to provide a pressure seal in the main outlet leg, enabling pressure stimulation through the offset outlet leg.
In accordance with another embodiment, the invention is a template positionable in a main well bore and configured for circulating fluids through the main well bore. The template includes a body, a tubular inlet leg, a tubular main outlet leg, and a tubular offset outlet leg, wherein the legs open into the body. An offset plug is positioned in the offset outlet leg. The template also includes a straddle assembly including a straddle tube having proximal and distal ends and proximal and distal seals positioned substantially at the proximal and distal ends. The proximal seal is mounted in the inlet leg and the distal seal is mounted in the main outlet leg to provide a continuous straddle assembly flow path through the body which substantially prevents fluid flow from the inlet leg into the offset outlet leg. Accordingly, a continuous downhole flow path is provided through the inlet leg, the straddle assembly, and the main outlet leg. The template is reconfigured from the fluid circulation configuration to the drilling configuration described above simply by removing the straddle assembly from the body, thereby providing the drill string path from the inlet leg to the offset outlet leg or to the main outlet leg.
In accordance with another embodiment, the invention is a template system positioned in a well bore and having a plurality of templates configured for circulating a fluid in the well bore. The system has an initial template and a first additional template, each of which are substantially as described above, including a body, a tubular inlet leg, a tubular main outlet leg, a tubular offset outlet leg, and a straddle assembly. The main outlet leg of the initial template is serially connected to the inlet leg of the first additional template to connect the continuous downhole flow path of the initial template to the continuous downhole flow path of the first additional template. The template system may further include second or more additional templates positioned in series, wherein the main outlet leg of the first additional template is serially connected to the inlet leg of the second additional template and the main outlet leg of the second additional template is serially connected to the inlet leg of the next additional template to interconnect the continuous downhole flow paths of all the templates.
In accordance with another embodiment, the invention is a template system positionable in a main well bore and having a plurality of templates configured for drilling at least one offset well bore through one of the templates from the main well bore. The system has an initial template and a first additional template, each of which are substantially as described above, including a body having a proximal face and a distal face, wherein the body encloses a primary chamber, a tubular inlet leg engaging the proximal face and aligned with an inlet opening in the proximal face, a tubular main outlet leg engaging the distal face and aligned with a main outlet opening in the distal face, and a tubular offset outlet leg engaging the distal face and aligned with an offset outlet opening in the distal face. The main outlet leg of the initial template is serially connected to the inlet leg of the first additional template. The template system may further include second or more additional templates positioned in series, wherein the main outlet leg of the first additional template is serially connected to the inlet leg of the second additional template and the main outlet leg of the second additional template is serially connected to the inlet leg of the next additional template to interconnect the continuous downhole flow paths of all the templates.
In accordance with another embodiment, the invention is a process for circulating a fluid through a template in a main well bore. The process provides a template including body, a tubular inlet leg, a tubular main outlet leg and a tubular offset outlet leg, wherein the legs open into the body. The template is positioned in a main well bore to form an annulus between the template and a face of the main well bore. A straddle assembly is releasably mounted in the template with the proximal seal positioned in the inlet leg and the distal seal positioned in the main outlet leg to provide a continuous straddle assembly flow path through the body. The straddle assembly substantially prevents fluid flow from the inlet leg into the offset outlet leg, such that a continuous downhole flow path is provided through the inlet leg, the straddle assembly, and the main outlet leg which excludes the offset outlet leg. The offset outlet leg is also plugged to prevent fluid communication between the main well bore and the offset outlet leg. A cement is injected in a distal direction into the downhole flow path and displaced proximally into the annulus by distally displacing the straddle assembly behind the cement. At least one by-pass tube is provided through the template which facilitates proximal displacement of the cement past the template. An offset well bore is drilled through the offset outlet leg which is thereafter completed through the offset outlet leg. The main well bore may also be extended by conveying a drill string through the main outlet leg.
In accordance with another embodiment, the invention is a process for circulating a fluid through a plurality of templates in a main well bore. The process provides an initial template and a first additional template, each including a body, a tubular inlet leg, a tubular main outlet leg and a tubular offset outlet leg, wherein the legs open into the body. The initial and first additional templates are serially positioned in a main well bore with the main outlet leg of the initial template connected to the inlet leg of the first additional template. An initial straddle assembly is releasably mounted in the initial template with the proximal seal positioned in the inlet leg and the distal seal positioned in the main outlet leg to provide a continuous straddle assembly flow path through the body and substantially prevent fluid flow from the inlet leg of the initial template into the offset outlet leg of the initial template. A first additional straddle assembly is releasably mounted in the first additional template with the proximal seal positioned in the inlet leg and the distal seal positioned in the main outlet leg to provide a continuous straddle assembly flow path through the body and substantially prevent fluid flow from the inlet leg of the first additional template into the offset outlet leg of the first additional template, such that a continuous downhole flow path is provided through the initial and first additional templates which excludes the offset outlet legs of the initial and first additional templates. The offset outlet legs of the initial and first additional templates are also plugged to prevent fluid communication between the main well bore and the offset outlet legs of the initial and first additional templates.
A distal extension tube is provided extending beyond the main outlet leg of the first additional template. The distal extension tube has a proximal end connected to the main outlet leg of the first additional template and a distal end opening into the main well bore. A cement is injected in a distal direction into the downhole flow path, through the distal extension tube and displaced proximally into an annulus between a face of the main well bore and the templates. Displacement of the cement into the annulus is effected by plugging the initial straddle assembly flow path to substantially prevent pressure communication between a proximal side of the initial straddle assembly and a distal side of the initial straddle assembly. A positive pressure differential is created on the proximal side of the initial straddle assembly to distally displace the initial straddle assembly which in turn displaces the cement. The first additional straddle assembly flow path is then plugged and the positive pressure differential on the proximal side of the initial straddle assembly is used to distally displace the first additional straddle assembly which further displaces the cement. Displacement of the initial straddle assembly also enables fluid communication between the inlet leg of the initial template and the offset outlet leg of the initial template. Similarly, displacement of the first additional straddle assembly enables fluid communication between the inlet leg of the first additional template and the offset outlet leg of the first additional template. The process may also provide second or more additional templates which are serially positioned the initial and first additional templates, wherein the main outlet leg of the first additional template is connected to the inlet leg of the second additional template and the main outlet leg of the second additional template is connected to the inlet leg of the next additional template. Second or more additional straddle assemblies are releasably mounted in the second or more additional templates with the proximal seal positioned in the inlet leg and the distal seal positioned in the main outlet leg to provide a continuous straddle assembly flow path through the body of the second or more additional templates and substantially prevent fluid flow from the inlet leg of the second or more additional templates into the offset outlet leg of the second or more additional templates. The second or more additional straddle assemblies are distally displaced to further displace the cement into the annulus.
A diverter is placed in the body of the initial template to define a drill string path from the inlet leg to the offset outlet leg of the initial template. An offset well bore is drilled from the main well bore by conveying a drill string through the offset outlet leg of the initial template. The offset well bore is also pressure stimulated through the offset outlet leg of the initial template. A diverter is similarly placed in the body of the first additional template to define a drill string path from the inlet leg to the offset outlet leg of the first additional template. An offset well bore is then drilled from the main well bore by conveying a drill string through the offset outlet leg of the first additional template. The offset well bore is also pressure stimulated through the offset outlet leg of the first additional template.
In accordance with another embodiment, the invention is a process for pressure stimulating a well bore through a template. The process provides a template having a tubular inlet leg, a tubular main outlet leg and a tubular offset outlet leg. The inlet leg and the main outlet leg are positioned in a main well bore and the offset outlet leg is positioned in an offset well bore extending from the main well bore. The main outlet leg is pressure sealed to withstand a pressure of at least about 3500 psi and the offset well bore is pressure stimulated through the offset outlet leg.